The Information Engineering Branch is responsible for developing and deploying all the production resources at NCBI. These include GenBank, Entrez, PubMed, BLAST, RefSeq, UniGene, PubMed Central, NCBI Bookshelf, LocusLink, annotation and assembly of complete genomes, and the NCBI software toolkit, among other things. These activities are closely interconnected and often data or personel from one activity are involved in others as well. These activities are a combination of research and development, and use expertise from biology and medicine, as well as from computer science and mathematics. NCBI production resources are widely used by more than 2,500,000 unique users a month, at a peak rate of almost 600 web hits a second. Users bulk download more than 400 gigabytes of data a day. This project supports many of the most heavily used public resources in biomedicine in the world.